Anders Magnusson wrote:
> 
> >
> > I noticed that the kernel is busy-waiting when idle. Can this not be
> > improved? I am used to the Motorola 68000 which has a WAIT instruction
> > that halts the CPU until an interrupt occurs...
> >
> Unfortunately no, the vax do not have any such instruction, busy-wait
> is the only solution.
> 
> -- Ragge
I have used the SIMH pdp-11 simulator and noticed that although the
software
(2.11BSD) uses the WAIT instruction. The processor load does not
decrease.
So it seems that even when the simulated processor is idle, the
simulator
is not. This is using Linux/386. I would like to have a pdp-11 running
BSD
or RT-11 in a window and then ignore them, but I always have to halt the
simulator or the host machine performance is like mud.

So even if the VAX had such an instruction, SIMH might not do the right
thing.

If anyone's experience is different, I would be interesting in knowing.

-chuck